Scale appears on Prof. Mardi Horowitz's website http://mardihorowitz.com/scales/impact_of_events_scale/. The link for permissions information did not work on 25th Oct 2016. Contact details are here: http://mardihorowitz.com/contact/. See also record 55 Impact of Events Scale - Revised. Note from this record: "Prof Horowitz has confirmed (by email) that people in non-profit research or clinical work may use the scale without permission [at?] Mardi Horowitz’s personal website." Prof Horowitz still seems to be the contact for this.